BMI Calculator
Body Mass Index with healthy-range guidance — updates as you type.
BMI is a screening tool, not a diagnosis — it does not distinguish muscle from fat. Athletes and pregnant women should interpret it with a professional.
Calculate your Body Mass Index instantly, in metric or imperial units, with your result plotted on a colour gauge, the healthy weight range for your exact height, and how far you are from it. Everything updates live as you type — no button, no sign-up, nothing stored.
How to use the BMI calculator
- Pick metric (cm/kg) or imperial (ft+in/lbs).
- Type your height and weight — the result appears immediately.
- Read your BMI, category, and the healthy weight range for your height.
Frequently asked questions
What is a healthy BMI?
18.5 to 24.9 for most adults, per WHO guidance. The calculator also shows the weight range that corresponds to it for your exact height.
Is BMI accurate for everyone?
No — it cannot tell muscle from fat, so muscular people read high and older adults can read low. Treat it as a starting point, not a verdict.
How is BMI calculated?
Weight in kilograms divided by height in metres squared. In imperial units: 703 × pounds ÷ inches².
Should I worry about a result outside the range?
A single number is not a diagnosis. If your BMI is persistently outside the healthy band, a doctor can look at the fuller picture — waist, diet, activity and history.
More health-adjacent maths: the age calculator and percentage calculator — all part of our free daily tools.